Bill Gates reads for an hour.

The Microsoft co-founder always makes time for reading before he goes to bed. He told The Seattle Times he reads for an hour, no matter how late it is. He manages to get through a book every week and also has a list of books he thinks everyone should read.

Arianna Huffington takes a hot bath.

The former co-founder and editor-in-chief of The Huffington Post Media Group decided to follow a strict sleeping routine after she collapsed in her office due to exhaustion and broke her cheekbone. She told CNBC she gets seven to nine hours of sleep a night by turning off all her electronic devices, taking a hot bath, and reading a book.

Michael Phelps climbs into an altitude chamber.

When he's training, Michael Phelps sleeps in a bedroom environment that mimics a high altitude, according to The Baltimore Sun. This decreases the amount of oxygen available, forcing his body to work harder to supply his muscles with oxygen.

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Gwyneth Paltrow often has a massage.

The actress and founder of lifestyle website Goop says she pays just as much attention to getting a good night's sleep as she does to her clean eating and wellness activities. According to Hello magazine, Paltrow fasts from 8 p.m. until breakfast the next day at 8 a.m., and recommends a foot or head massage to de-stress before going to bed.

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Elon Musk cuts back on caffeine.

To keep up with his responsibilities as CEO of SpaceX and Tesla, Elon Musk used to drink eight cans of Diet Coke and two cups of coffee every day. That's a lot of caffeine. He told a Reddit AMA in 2015 that it was making him too wired, so he now steers away from caffeine for six hours before bedtime. He also tracks his sleep with his phone.

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Barack Obama watches The Daily Show.

When the 44th President of the US was in the White House, he didn't have time for particularly healthy bedtime routines and was often up into the early hours of the night. However, he told Rolling Stone that when he could, he would unwind with a good book, tuck in his daughters, then occasionally watch an episode of The Daily Show.

Stephen King washes his hands.

The horror and science fiction writer has a few unusual bedtime habits. He said in Haunted Heart: The Life and Times of Stephen King that he has the same routine every night: "I brush my teeth, I wash my hands. Why would anybody wash their hands before they go to bed? I don't know." He also said the pillows have to be arranged a certain way.

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Mariah Carey surrounds herself with humidifiers.

Thomson Reuters

Carey told Interview magazine she has to sleep "15 hours to sing the way I want to." To achieve this, she has several humidifiers in her bedroom, which add moisture to dry air. They are allegedly good for sore throats. "Basically, it's like sleeping in a steam room," she said.

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Kenneth Chenault makes a to-do list for the next day.

The CEO and Chairman of American Express creates a to-do list for the following day, according to Fast Company. Before going to bed, Chenault writes down three things he wants to accomplish the next day.

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Eminem shuts out all the light.

In 2012, The Sun reported that rapper Eminem wrapped tinfoil around the windows of his hotel room to keep out the light. A source apparently said: "The noise and darkness gets Eminem the best night's sleep. He uses the technique as he's always jumping time-zones."